Congestion control method for packet switching apparatus

Abstract

One technique of a congestion control method for packet switching apparatuses, in which a plurality of priority data indicative of different demands, such as a first priority data indicative of immediateness priority and a second priority data indicative of necessity priority, are attached to each packet. In congestion of a packet queue, such control is carried out that such a packet as having the high first immediateness priority is rearranged as located in the front part of the queue while such a packet as having the high first immediateness priority but having the low second necessity priority is first discarded according to the first and second priority data of the packets, whereby major demands for the each packet are concurrently satisfied. For example, a packet of data transferred between telephone set terminals has a strong immediateness demand but has a relatively weak necessity demand, whereas, a packet of data transferred between data terminals has a relatively weak immediateness demand but has a strong necessity demand.

What is claimed is: 
     
       1. In a packet switching apparatus interconnected by associated communication lines to one or more other packet switching apparatuses, wherein data packets are output from various types of terminals and are temporarily held in a queue for exchange between the packet switching appartuses, a congestion control method comprising the steps of: attaching a plurality of types of priority data indicating different priorities for different demands to each of the data packets; and   controlling the queue when a new data packet is input to the queue to satisfy major demands for the data packets concurrently according to said plurality of types of attached priority data of said new data packet and of all the data packets held in the queue.   
     
     
       2. A congestion control method as set forth in claim 1, wherein said plurality of types of priority data comprise a first priority data indicative of the degree of immediateness priority and a second priority data indicative of the degree of necessity of priority, and the queue controlling step further includes rearranging the order of the data packets in said queue so that the data packets attached with a higher first priority data are sequentially arranged closer to a top part of the queue, and determining a discard order of the data packets in the queue so that the data packets attached with said lower second priority data are discarded on a preferential basis. 
     
     
       3. A congestion control method as set forth in claim 2, wherein said data packets to be exchanged and transferred include a voice packet transferred between telephone set terminals and a terminal data packet transferred between data terminals, and the attaching step includes attaching said voice data packet with a high first priority data and a low second priority data, and attaching said terminal data packet with a low first priority data and a high second priority data. 
     
     
       4. A congestion control method as set forth in claim 1, wherein the queue has a predetermined capacity and the queue controlling step includes setting a threshold value according to the capacity of said queue for determining whether said queue is in a congestion state, and includes further controlling the queue to satisfy major demands for the data packets concurrently when the number of data packets temporarily held in the queue exceeds said threshold value. 
     
     
       5. A congestion control method as set forth in claim 2, wherein the queue has a predetermined capacity and the queue controlling step includes setting a threshold value according to the capacity of said queue for determining whether said queue is in a congestion state, and includes further controlling the queue to satisfy major demands for the data packets concurrently when the number of data packets temporarily held in the queue exceeds said threshold value, thereby sequentially arranging the data packets attached with said higher first priority data to the top part of the queue and discarding the data packets attached with said lower second priority data on a preferential basis. 
     
     
       6. A congestion control method as set forth in claim 3, wherein the queue has a predetermined capacity and the queue controlling step includes setting a threshold value according to the capacity of said queue for determining whether said queue is in a congestion state, and includes further controlling the queue is to satisfy major demands for the data packets concurrently when the number of data packets temporarily held in the queue exceeds said threshold value, thereby sequentially arranging the data packets attached with said higher first priority data closer to the top part of the queue and discarding the data packets attached with said lower second priority data on a preferential basis.